1. Field of the Invention
The present invention relates to a semi-transmissible reflector and a semi-transmission type polarizer used in a liquid-crystal display device (hereinafter referred to also as “LCD”) and a liquid-crystal display device using these plates.
2. Description of the Related Art
LCD has been used in a personal computer or the like. The demand for LCD has increased rapidly in recent years. The application of LCD has been widened so that LCD has begun to be used for the purpose of a monitor in recent years.
For example, a polarizer used in LCD is produced as follows. After a dyeing step of dyeing a polyvinyl alcohol (hereinafter referred to also as “PVA”) film with dichromatic iodine or dye, a crosslinking step of crosslinking the film with boric acid, borax or the like and a drawing step of uniaxially drawing the film, the polyvinyl alcohol film is dried and stuck onto a protective layer of a triacetyl cellulose (hereinafter referred to also as “TAC”) film or the like.
A biaxially oriented polymer substrate or a filler-containing polymer substrate has been heretofore used as the substrate for the semi-transmissible reflector used in LCD.
When a semi-transmissible reflector constituted by a substrate of this type is used in combination with a backlight having polarizing characteristic, there is however a problem that coloring occurs because the influence of retardation reduces transmittance of light with a specific wavelength. A monochromatic liquid-crystal display device is tolerant of weakly uniform coloring but is not tolerant of ununiform coloring. A color liquid-crystal display device is not tolerant of even uniform coloring. Therefore, how to prevent such coloring is a large problem. To solve this problem, reduction in transmittance of light rays emitted from a backlight light source so as to be used as transmitted light rays needs to be suppressed to be not larger than 10% at maximum, preferably not larger than 5%, more preferably not larger than 1% when a semi-transmission type polarizer is used in combination with a backlight having polarizing characteristic.